This invention relates to long-term epidural catheters adapted for use in pain management, e.g. to relieve intractable pain in cancer patients.
Heretofore, a number of different methods have been utilized to relieve intractable pain. These include palliative or "curative" therapy (i.e. surgery, radiation therapy or chemotherapy), systemically administered narcotics, transcutaneous electrical stimulation, nerve blocks, rhizotomy, radiofrequency, induced lesions, epidural or dorsal column electrical stimulation, and central nervous system neurosurgical intervention, e.g. cordotomy, thalamotomy, acupuncture, and hypnosis.
While systems for relieving cancer pain by the administration of morphine using an indwelling system have been disclosed in the literature for some time, e.g. in "Cancer Pain Relieved by Long-Term Epidural Morphine With Permanent Indwelling Systems for Self-Administration", by C. Poletti et al, Journal of Neurosurgery, Vol. 55, October, 1981, pp 581-584, it has only been relatively recently that the treatment of intractable pain by epidural infusion of a narcotic has gained acceptance in a number of medical centers.
More recently, the responsibility for the treatment and control of pain has been moving from the surgeon and general practitioner to the anesthesiologist. As anesthesiologists are broadening their practice outside the operating room suite, they are managing acute pain in the post-operative areas and chronic pain in the clinics.
In the past five years, approximately one thousand pain clinics have been established, about 60% of which are headed by anesthesiologists. A majority of these pain clinics treat cancer pain and many are affiliated with a cancer treatment center.
One of the treatment modalities gaining in popularity for terminal cancer pain management is the tunneled epidural catheter. This procedure provides better analgesia without frequent injections or cumbersome I.V. equipment, present fewer complications, and are generally better tolerated by the patient. Epidural narcotic administration works well because there are opiate receptors located all along the spinal cord. Thus, the narcotic can act directly on the receptors, producing localized analgesia without more blockage. This in turn allows for lower dosages and minimizes cerebral and systemic effects.
The tunneled epidural catheters currently on the market are what may be termed a "two-piece" catheter consisting of a first or distal piece for introduction into the epidural space, e.g. as close to the dorsal midline as possible, and a second or proximal piece which is tunneled subcutaneously between the dorsal paravertebral entry site of the first piece and a lateral or ventral exit site from the skin where it is to be connected to a syringe or other source of the narcotic to be administered for pain management.
The tunneling may be effected in the direction from the exit site to the first catheter piece or, alternatively, it may be the reverse, namely from the first catheter piece to the exit site. In either case, the proximal end of the first or distal piece is secured in fluid-tight relationship to the distal end of the second or distal catheter piece and sutured in place to provide a tunneled long-term epidural catheter extending from the dorsal point where it is introduced into the epidural space to a desired location on the side or front of the patient for more comfortable and accessible hook-up to a source of the narcotic to be administered.
Illustrative of the current state of the art on tunneled epidural catheters is the Du Pen (TM) Long-Term Epidural Catheter commercially available form Davol Inc., Subsidiary of C. R. Bard, Inc. and reported in "A New Permanent Exteriorized Epidural Catheter for Narcotic Self-Administration to Control Cancer Pain" by Dr. Stuart L. DuPen et al, CANCER, Vol. 59, No. 5, Mar. 1, 1987, pp 986-993.
As stated therein, the new exteriorized epidural catheter consists of three pieces: (1) an epidural segment that is placed through a needle into the epidural space; (2) an exteriorized line equipped with an external luer connector and a subcutaneous Dacron cuff; and (3) a small splice segment to join the two catheter segments. Both the epidural and percutaneous lines are prepared from radiopague silicone rubber.
According to the protocol described collectively in the DuPen article and/or the Davol product literature, under local infiltration anesthesia, 7 cm paravertebral incision is made from the L-2 dorsal spine down to the paravertebral fascia, for needle placement and catheter splicing. A 14-gauge Hustead needle is then passed into the dorsal midline epidural space. With the aid of a guidewire, the epidural segment is advanced to the desired level within the epidural space. Epidural placement can be verified by ease of catheter passage, fluoroscopy and sensory blockade resulting from a 12-ml epidural dose of 2% lidocaine. Following placement of the epidural segment, the needle and guidewire are withdrawn and the proximal end of the catheter is trimmed to length.
The exteriorized line is tunneled from a subcostal location on the mid-nipple line (where it is easier to see and use) around to the lower end of the paravertebral incision. It is positioned with the Dacron cuff 5 cm internal (subcutaneous) from the exit site where the proximal end of the exteriorized line comes through the skin.
The small splice segment or catheter connector is then used to connect the two catheter ends together, using non-absorbable bridge ties to secure the catheter ends to the connector. To avoid damaging the catheter segments during this splicing operation, soft plastic sleeves provided with the "Du Pen" tray are slipped over the forceps tips for holding the ends. The splice segment is then secured to the supraspinus tissue to maintain a gentle curvature and to avoid kinking.
A conventional filter used for morphine injection, e.g. a Millex-OR 0.22 um filter unit from Millipore Corporation, is then attached to the luer connector and secured with tape. A dressing is then applied over the exit site and the filter may then be taped to the patient's skin.
The tunneled epidural catheter is then ready for connecting to the narcotic source.
While tunneled epidural catheters of the foregoing "two-piece" description provide a highly effective and efficacious means for relieving intractable pain originating below the cranial nerves, they nevertheless suffer from certain inherent disadvantages due to the manipulative steps required to assemble and prepare the catheter for drug administration into the epidural space, namely:
1. The catheter consists of two segments which have to be connected together at the paravertebral point where the epidural catheter component is introduced into the epidural space;
2. The dexterity involved in guiding the tunneler from the exit site to the paravertebral incision point and then bringing the described exteriorized line (proximal segment) in juxtaposition with the epidural segment for connection.
3. The necessity of trimming the segments to length for connection.
4. A third component, e.g. a connector, splicer or equivalent element is required to perfect the connection;
5. The procedural recommendation of suturing the connection to the supraspinous tissue to guard against any adverse movement of the distal end of the epidural segment positioned within the epidural space;
6. The fact that a relatively large paravertebral incision is required to make the necessary connection of the two catheter segments and to embed the resulting connection subcutaneously; and
7. The fact that during the surgical aspect of the catheterization, the recommended procedure requires fitting a pair of soft flexible sleeves provided in the catheter tray onto the forceps used to hold the catheter in order to avoid damage while performing the above steps;
As was heretofore mentioned, there is a recent trend for the responsibility for the treatment and control of pain to move from the surgeon to the anesthesiologist. The foregoing disadvantages are particularly apparent when one considers that by training, experience and personal inclination, the anesthesiologist is far more comfortable with a needle than he is with a scalpel and suture.
Stated simply, the task of the present invention is to provides a tunneled long-term epidural catheter which obviates the aforementioned disadvantages.